I found this post by Barbara over at Investigating Obama:
One point people have made is that because the man Obama’s mother “married” first was actually Muslim but more to the point ALREADY MARRIED to another woman, then although by Muslim law she was married to that man, (since by Muslim law a man is allowed to have 4 wives), still, by American law, a man is allowed to have only one wife at a time, therefore since Obama senior was already married, his “marriage” to Stanley Ann Dunham never truly occurred legally by American law.
Therefore, Stanley Ann Dunham was in fact an unwed mother.
Because she was an unwed mother, by US law, in that situation, birthright is ONLY given through the mother.
The unwed mother would have had to have resided in the United States for the year preceding the birth of her child.
However, since Stanley Ann Dunham says that she lived in Hawaii for the year preceding little Barack Obama II’s birth, she could NOT have passed on US citizenship to him. And this is why:
Hawaii had NOT become joined to the United States at that time, and was not for several years afterwards.
Therefore, Barack Obama II was NOT given ANY US citizenship at birth.
Therefore at least in terms of his birth, Barack Obama II has no US natural born citizenship.
As such, Barack Obama II has NO eligibility to run for President of the United States.
Darn those anti-bigamy laws anyway!
Barack Obama was born in 1961 and Hawaii became a state in 1959. Exercise for the reader: which is earlier: 1959 or 1961? How can you do this on a calculator? Make a guess as to which one is later and punch it into your calculator, then press the minus sign (-) then punch in the second number and press =. If there is a “-” next to the answer then you guessed wrong, if not you were right!